The present invention is related to storage media, and more particularly to systems and methods for aligning a read/write head assembly in relation to a storage medium.
A typical storage medium includes a number of storage locations where data may be stored. Data is written to the medium within areas designated for user data by positioning a read/write head assembly over the storage medium at a selected location, and subsequently passing a modulated electric current through the head assembly such that a corresponding magnetic flux pattern is induced in the storage medium. To retrieve the stored data, the head assembly is positioned over a track containing the desired information and advanced until it is over the desired data. The previously stored magnetic flux pattern operates to induce a current in the head assembly, and the induced current may then be converted to an electrical signal representing the originally recorded data.
The storage locations on the storage medium are typically arranged as a serial pattern along concentric circles known as tracks. FIG. 1 shows a storage medium 100 with two exemplary tracks 150, 155 indicated as dashed lines. The tracks are segregated by servo data written within wedges 160, 165. The servo data includes data and supporting bit patterns that are used for control and synchronization of the read/write head assembly over a desired storage location on storage medium 100. In particular, the servo data traditionally includes a preamble pattern followed by a single sector address mark (SAM). The SAM is followed by a Gray code, and the Gray code is followed by burst information. It should be noted that while two tracks and two wedges are shown, hundreds of each would typically be included on a given storage medium. Further, it should be noted that a sector may have two or more burst fields depending upon the approach selected for determining position error.
Conventional servo data utilizes the preamble field to adjust timing and gain loops in an effort to synchronize sampling to data written to the storage medium. After the timing loops and gain loops are stable, the SAM, the Gray code and the burst information are processed to determine location on the storage medium and to generate a position error signal. Accurate determination of the timing and gain from the preamble is critical to proper processing of the servo data. For example, where the timing is not accurate, any position error signal will be correspondingly inaccurate. This inaccuracy can cause an increase in bit error rate due to improper positioning of the read/write head assembly in relation to the storage medium. To increase the accuracy of the timing and gain loops, longer preambles may be chosen. However, increasing the preamble length causes a corresponding reduction in storage density on the storage medium.
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods for increasing the accuracy of position error determination.